Pants-type disposable wearing article

ABSTRACT

A pants-type disposable wearing article includes leg-circumferential first elastic members attached to crotch region&#39;s lateral margins of an outer sheet and waist-circumferential second elastic members attached to waist regions&#39; upper margins of the outer sheet. The elastic members are joined to the sheet while the sheet and the second elastic members are stretched at given extension ratios, respectively, in a transverse direction and the first elastic members is stretched at a given extension ratio in the leg-circumferential direction so that the sheet and the first elastic members may have substantially the same leg-circumferential dimensions after these sheet and first elastic members have been relaxed and the sheet and the second elastic members may have substantially the same transverse dimensions after these sheet and second elastic members have been relaxed. In addition, the waist regions&#39; upper margins and the crotch region&#39;s lateral margins are substantially planar.

This application is a continuation of International Application No.PCT/JP03/000915 filed Jan. 30, 2003, which claims priority to JapaneseApplication Nos. 2002-020804 filed Jan. 30, 2002 and 2003-018205 filedJan. 28, 2003, all of which are hereby incorporated by reference hereinin their entirety.

BACKGROUND OF THE INVENTION

This invention relates to a pants-type disposable wearing article forabsorption and containment of bodily discharges.

Conventional pants-type disposable wearing articles, for example, anarticle disclosed in Japanese Utility Model Unexamined Publication No.1991-122824A comprise an elastically stretchable liquid-pervioustopsheet lying on a body facing side, a liquid-impervious backsheetlying on an undergarment facing side and a liquid-absorbent coreinterposed between these top- and backsheets so as to define front andrear waist regions opposed to each other, a crotch region extendingbetween the front and rear waist regions, a waist-opening and a pair ofleg-openings.

The aforesaid article has waist regions' upper margins extending acrossthe front and rear waist regions in a transverse direction, waistregions' lateral margins extending in a longitudinal direction andcrotch region's lateral margins extending in a leg-circumferentialdirection. In this article, the waist regions' lateral margins are putflat and joined together in the vicinity of the outermost edges of theselateral margins by means of a plurality of welding lines arrangedintermittently in the longitudinal direction. A plurality of elasticmembers extending in the transverse direction are contractibly attachedto the respective waist regions' upper margins. Similarly, a pluralityof elastic members extending in the leg-circumferential direction arecontractibly attached to the crotch region's lateral margins. Theelastically stretchable top- and backsheets cooperate with thewaist-circumferential elastic members to tighten the wearer's waistwhile the top- and backsheets cooperate with the leg-circumferentialelastic members to tighten the wearer's legs so as to eliminate apossibility that the article might unintentionally slip down along thewearer's waist and bodily discharges might leak out beyond the crotchregion's lateral margins.

In the case of the aforesaid article, the waist regions' upper marginsare formed with a plurality of irregular wrinkles or gathers undulatingin a thickness direction of the top- and backsheets due to contractionof the waist-circumferential elastic members in the transversedirection. Similarly, the crotch region's lateral margins are formedwith a plurality of irregular wrinkles or gathers undulating in thethickness direction of the top- and backsheets due to contraction of theleg-circumferential elastic members in the leg-circumferentialdirection. Formation of such wrinkles or gathers along the waistregions' upper margins and the crotch region's lateral marginsnecessarily results in gaps between the wearer's body and the waistregions' upper margins and between the wearer's body and the crotchregion's lateral margins. Consequently, bodily discharges might leak outbeyond the waist regions' upper margins and the crotch region's lateralmargins through those gaps even if the elastic members adequatelytighten the wearer's waist and legs. Furthermore, the wrinkles orgathers formed along the waist regions' upper margins and the crotchregion's lateral margins may give the wearer more or less uncomfortablefeeling and sometimes mark compression traces on the wearer's body.

SUMMARY OF THE INVENTION

In view of the problems described above, it is an object of thisinvention to provide a pants-type disposable wearing article improved sothat both the waist regions' upper margins and the crotch region'slateral margins are free from formation of a plurality of irregularwrinkles or gathers even after the elastic members attached to thesemargins have been relaxed and neither leakage of bodily dischargesbeyond the waist regions' margins and the crotch region's lateralmargins nor uncomfortable feeling experienced by the article wearer isconcerned.

The object set forth above is achieved, according to this invention, bya pants-type disposable wearing article comprising an elasticallystretchable outer sheet defining front and rear waist regions opposed toeach other and a crotch region extending between these waist regions,and a liquid-absorbent panel attached to an inner surface of the outersheet and extending between the front and rear waist regions, the outersheet having waist regions' upper margins extending in the front andrear waist regions in a transverse direction, waist-circumferentiallateral margins extending in a longitudinal direction and crotchregion's lateral margins extending in the crotch region in theleg-circumferential direction, the front and rear waist regions beingconnected along the waist-circumferential margins so as to define awaist-opening and a pair of leg-openings, and first elastic membersextending in the leg-circumferential direction are attached to thecrotch region's lateral margins of the outer sheet.

The outer sheet and the first elastic members are joined together whilethe outer sheet is stretched at an appropriate given stretching ratio inthe transverse direction and the first elastic members are stretched atan appropriate given stretching ratio in the leg-circumferentialdirection so as to ensure that the outer sheet and the first elasticmembers have substantially the same dimensions as measured in theleg-circumferential direction after these outer sheet and first elasticmembers have been relaxed and that the crotch region s lateral marginsare substantially planar without undulation in a thickness direction ofthe outer sheet.

This invention includes the following embodiments.

Waist-circumferential second elastic members extending in the transversedirection are attached to the waist regions' upper margins of the outersheet and the outer sheet and the second elastic members are bondedtogether while the outer sheet is stretched at an appropriate givenstretching ratio and the second elastic members are stretched at anappropriate stretching ratio both in the transverse direction so as toensure that the outer sheet and the second elastic members havesubstantially the same dimensions as measured in the transversedirection after these outer sheet and second elastic members have beenrelaxed and that the waist regions' upper margins are substantiallyplanar without undulation in a thickness direction of the outer sheet.

A transverse stretch stress in the waist regions' upper margins of theouter sheet is higher than a leg-circumferential stretch stress in thecrotch region's lateral margins of the outer sheet and also than atransverse stretch stress in a portion of the outer sheet except thewaist regions' upper margins and the crotch region's lateral margins.

The leg-circumferential stretch stress in the crotch region's lateralmargins in the outer sheet is higher than the transverse stretch stressin the portion of the outer sheet except the waist regions' uppermargins and the crotch region's lateral margins.

The outer sheet is formed by a composite nonwoven fabric layer composedof two elastically stretchable hydrophobic fibrous nonwoven fabriclayers placed upon each other and the first and second elastic membersare interposed between these nonwoven fabric layers.

The outer sheet is formed by a composite sheet composed of anelastically stretchable hydrophobic fibrous nonwoven fabric layer and abreathable liquid-impervious plastic film joined together and the firstand second elastic members are interposed between the nonwoven fabriclayer and the film.

The panel comprises a liquid-pervious topsheet lying on a body facingside, a liquid-impervious backsheet lying on an undergarment facing sideand a liquid-absorbent core interposed between the top- and backsheets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway perspective view depicting a wearingarticle as one embodiment of this invention;

FIG. 2 is a developed plan view depicting the article of FIG. 1 in thestate before front and rear waist regions are connected to each otheralong transversely opposite lateral margins of these waist regions;

FIG. 3 is a sectional view taken along a line III-III in FIG. 2;

FIG. 4 is a sectional view taken along a line IV-IV in FIG. 2;

FIG. 5 is a plan view of an outer sheet;

FIG. 6 is a diagram schematically illustrating an example of aproduction line for the outer sheet;

FIG. 7 is a plan view depicting the inner sheet as before the innersheet is divided in two; and

FIG. 8 is a diagram schematically illustrating a manner in which a panelis attached to the outer sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Details of a pants-type disposable wearing article according to thisinvention will be more fully understood from the description givenhereunder in reference with the accompanying drawings.

FIG. 1 is a perspective view of an wearing article 1 illustrated as oneembodiment of this invention, FIG. 2 is a partially cutaway plan viewdepicting this article 1 in its state prior to connection of front andrear waist regions to each other along transversely opposite waistregions' lateral margins, and FIGS. 3 and 4 are sectional views takenalong lines III-III and IV-IV in FIG. 2, respectively. In FIGS. 1 and 2,a transverse direction is indicated by an arrow L, a longitudinaldirection is indicated by an arrow M and a leg-circumferential directionis indicated by an arrow N (only in FIG. 1). Expression “inner surfaces”of an outer sheet 2 and top- and backsheets 19, 20 should be understoodto be the surfaces thereof facing a core 21 and expression “outersurfaces” of these sheets 2, 19, 20 should be understood to be thesurfaces thereof facing away from the core 21.

The article 1 comprises the elastically stretchable andliquid-impervious outer sheet 2, first elastic members 3 extending inthe leg-circumferential direction and second elastic members 4 extendingin the waist-circumferential direction both attached to the outer sheet2, and a liquid-absorbent panel 5 attached to the inner surface of theouter sheet 2. The article 1 is of pants-type having a waist-opening 6and a pair of leg-openings 7 lying below the waist-opening 6.

The outer sheet 2 is formed by a composite nonwoven fabric comprisingtwo layers 8, 9 of elastically stretchable hydrophobic fibrous nonwovenfabric placed upon each other and elastically stretchable in thelongitudinal and transverse directions as well as in theleg-circumferential direction. The nonwoven fabric layers 8, 9 haverespective surfaces opposed and intermittently bonded to each other bymeans of adhesive (not shown). The outer sheet 2 defines a front waistregion 10 and a rear waist region 12 opposed to each other and a crotchregion 11 extending between these waist regions 10, 12. The outer sheet2 is divided into a first outer sheet section 2 a lying on the side ofthe front waist region 10 and a second outer sheet section 2 b lying onthe side of the rear waist region 12.

The outer sheet 2 has waist regions' upper margins 13 lying outsidelongitudinally opposite ends 5 a of the panel 5 so as to extend acrossthe front and rear waist regions 10, 12 in the transverse direction,waist regions' lateral margins 14 lying outside transversely oppositeside edges 5 b of the panel 5 in the front and rear waist regions 10, 12so as to extend in the longitudinal direction, crotch region's lateralmargins 15 lying outside the transversely opposite side edges 5 b in thecrotch region 11 so as to extend in the leg-circumferential direction,and lower margins 16 lying in the crotch region 11 so as to extendacross the panel 5.

As will be seen in FIG. 2, the crotch region's lateral margins 15destined to define peripheries of the respective leg-openings 7 curveinward as viewed in the transverse direction of the article 1 as thesecrotch region's lateral margins 15 get nearer to a longitudinally middlezone 11 a of the crotch region 11. In other words, a transversedimension of the lower margin 16 is smaller than that of the uppermargin 13. These two lower margins 16 opposed to each other in thelongitudinally middle zone 11 a of the crotch region 11 are spaced fromeach other by a given dimension. In the outer sheet 2, The respectivesheet sections 2 a, 2 b are put flat together along the waist regions'lateral margins 14 thereof and joined together in the vicinity of sideedges 17 of these waist regions lateral margins 14 by means of aplurality of welding lines 18 arranged intermittently in thelongitudinal direction.

It is not essential to divide the outer sheet 2 into the first andsecond outer sheet sections 2 a, 2 b but the lower margins 16 of thesesheet sections 2 a, 2 b may be contiguous to each other in the crotchregion 11 so as to define the whole area of the crotch region 11. Inthis case, the outer sheet 2 has the waist regions' upper margins 13 andthe waist regions' lateral margins 14 extending in the front and rearwaist regions 10, 12 and the crotch region's lateral margins 15extending in the crotch region 11.

The first elastic members 3 associated with the respective leg-openingsare arranged along the crotch region s lateral margins 15 of the crotchregion so as to extend in the leg-circumferential direction. The firstelastic members 3 comprise a plurality of elastic threads spaced onefrom another by a given dimension in the transverse direction. Thesecond elastic members 4 associated with the waist-opening are arrangedalong the waist regions' upper margins 13 so as to extend in thetransverse direction. The first elastic members 3 and the second elasticmembers 4 are interposed between the nonwoven fabric layers 8, 9constituting the outer sheet 2 and secured to the respective surfaces ofthese nonwoven fabric layers 8, 9 opposed to each other by means ofadhesive (not shown) It should be understood that the desired effect canbe achieved by securing these elastic members 3, 4 to the nonwovenfabric layers 8, 9 only along the waist regions' lateral margins 14 andthe respective lower margins 16 of the outer sheet sections. In otherwords, it is not essential to secure these elastic members 3, 4 to thenonwoven fabric layers 8, 9 in a regions defined between those lateralmargins 14 and lower margins 16.

The outer sheet 2 and the first elastic members 3 are joined togetherwhile the sheet 2 is stretched at a given stretching ratio in thetransverse direction and the first elastic members 3 are stretched at agiven stretching ratio in the leg-circumferential direction. After thesheet 2 and the first elastic members 3 have been joined together inthis manner, such stretching force is released and both the outer sheet2 and the first elastic members 3 are allowed to contract. After thestretching force has been released, the outer sheet 2 and the firstelastic members 3 restore respective initial leg-circumferentialdimensions which are substantially equal one to another. Consequently,there is no possibility that the crotch region's lateral margins 15 ofthe outer sheet 2 might be formed with a plurality of irregular wrinklesor gathers due to the contraction of the first elastic members 3. Inaddition, there is no possibility that the crotch region's lateralmargins 15 of the outer sheet 2 might undulate in a thickness directionof the sheet 2, so these lateral zones 15 destined to define theperipheries of the leg-openings are substantially planar.

The outer sheet 2 has a predetermined residual strain causing adimensional difference (i.e., hysteresis error) between dimension of theouter sheet 2 before it is stretched and the dimension thereof after itwas stretched and then allowed to contract. Similarly, the first elasticmembers 3 have a predetermined residual strain causing a dimensionaldifference (i.e., hysteresis error) between the dimension of the firstelastic members 3 before these members 3 are stretched and the dimensionthereof after these members 3 have been stretched and then allowed tocontract. In general, the residual strain exhibited by the outer sheet 2is more or less different from the residual strain exhibited by thefirst elastic members 3 because the residual strain depends on variousfactors such as quality of material, length, width and thickness.

It is assumed that the outer sheet 2 and the first elastic members 3respectively exhibiting different residual strains are joined togetherwhile these outer sheet 2 and elastic members 3 are stretched at one andsame stretching ratio and then allowed to contract. In this case, adifferential residual strain between these outer sheet 2 and elasticmembers 3 will inevitably result in a dimensional difference betweenthese outer sheet 2 and elastic members 3 after they have been allowedto contract. Eventually, the circumferential lateral margins 15 of thewaist regions will be formed with wrinkles or gathers. To overcome thisproblem, respective stretching ratios of the outer sheet 2 and the firstelastic members 3 are preadjusted in the article 1 according to thisinvention by taking account of the residual strains peculiar to theouter sheet 2 and the first elastic members 3 so that the outer sheet 2and the first elastic members 3 may have substantially the samedimensions in the leg-circumferential direction. In this way, there isno anxiety that any significant wrinkles or gathers might appear alongthe crotch region's lateral margins 15 destined to define theperipheries of the respective leg-openings even after the outer sheet 2and the first elastic members 3 have contracted.

The outer sheet 2 and the second elastic members 4 are joined togetherwhile the sheet 2 is stretched at a given stretching ratio in thetransverse direction and the second elastic members 4 are stretched at agiven stretching ratio in the transverse direction. After the sheet 2and the second elastic members 4 have been joined together in thismanner, such stretching force is released and both the outer sheet 2 andthe second elastic members 4 are allowed to contract. After thestretching force has been released, the outer sheet 2 and the secondelastic members 4 restore respective initial transverse dimensions whichare substantially equal one to another. Consequently, there is nopossibility that the waist regions' lateral margins 13 of the outersheet 2 might be formed with a plurality of irregular wrinkles orgathers due to the contraction of the second elastic members 4. Inaddition, there is no possibility that the waist regions' lateralmargins 13 of the outer sheet 2 might undulate in a thickness directionof the sheet 2, so these lateral zones 13 destined to define theperipheries of the waist-opening are substantially planar.

The second elastic members 4 have a predetermined residual straincausing a dimensional difference (i.e., hysteresis error) between thedimension of the second elastic members 4 before these members 4 arestretched and the dimension thereof after these members 4 have beenstretched and then allowed to contract. As has been described justabove, the residual strain exhibited by the outer sheet 2 is more orless different from the residual strain exhibited by the second elasticmembers 4 because the residual strain depends on various factors such asquality of material, length, width and thickness.

Now it is assumed that the outer sheet 2 and the second elastic members4 respectively exhibiting different residual strains are joined togetherwhile these outer sheet 2 and elastic members 4 are stretched at one andsame stretching ratio and then allowed to contract. In this case, adifferential residual strain between these outer sheet 2 and elasticmembers 4 will inevitably result in a dimensional difference betweenthese outer sheet 2 and elastic members 4 after they have been allowedto contract. Eventually, the waist regions' upper margins 13 will beformed with wrinkles or gathers. To overcome this problem, respectivestretching ratios of the outer sheet 2 and the second elastic members 4are preadjusted in the article 1 according to this invention by takingaccount of the residual strains peculiar to the outer sheet 2 and thesecond elastic members 4 so that the outer sheet 2 and the secondelastic members 4 may have substantially the same dimensions in thetransverse direction. In this way, there is no anxiety that anysignificant wrinkles or gathers might appear along the waist regions'upper margins 13 even after the outer sheet 2 and the second elasticmembers 4 have contracted.

Should the outer sheet 2 and the first and second elastic members 3, 4exhibit substantially the same residual strains, the sheet 2 and theseelastic members 3, 4 maybe joined together while these sheet 2 andelastic members 3, 4 are stretched at a same ratio. This is for thereason that, if these sheet 2 and elastic members 3, 4 are joinedtogether while they are stretched at different ratios, respectively, acontractile force of the one would shorten the other, resulting in thatthe waist regions' upper margins 13 as well as the crotch region'slateral margins 15 would be formed with wrinkles or gathers.

It is possible to provide the front and rear waist regions 10, 12 of theouter sheet 2 with a plurality of auxiliary third elastic membersextending in the transverse direction between the first elastic members3 and the second elastic members 4. In this case, the stretching ratiosat which the sheet 2 and the third elastic members are stretched in thetransverse direction in the course of bonding these sheet 2 and thirdelastic members together may be appropriately preadjusted to ensure thatthese sheet 2 and third elastic members have substantially the sametransverse dimensions after these sheet 2 and third elastic members havebeen relaxed.

Preferably, the outer sheet 2 exhibits a stretch stress of 0.05-0.5N/25mm as the outer sheet 2 is stretched at a ratio of 10-20% and has abasis weight of 20-150 g/m². The elastically stretchable nonwoven fabriclayers 8, 9 constituting are preferably stretchable by 100-400% in thelongitudinal, transverse and waist-circumferential directions. Thesenonwoven fabric layers 8, 9 exhibit a same residual strain.

A stock material for the elastically stretchable nonwoven fabric layers8, 9 may be selected from a series of products obtained by melt blown-,spun bond- and spun lace-processes. The component fibers may be, forexample, elastically stretchable fibers obtained by a melt-spinningthermoplastic elastomer resin. It is desirable for the nonwoven fabriclayers 8, 9 that respective test pieces (each having a diameter of 1 mmand a length of 3 mm) thereof exhibit a residual strain of 16% or lessafter these test pieces have been stretched by 50% (stretched twice atan ambient temperature of 20° C.). Now a stress exhibited by these testpieces (each having a diameter of 1 mm and a length of 100 mm) afterthese test pieces have been stretched by 50% (stretched once at astretching rate of 100 mm/min at an ambient temperature of 40° C.) isrepresented by S1 while a stress exhibited by these test pieces (eachhaving a diameter of 1 mm and a length of 100 mm) after these testpieces have been stretched by 50% (stretched once at an ambienttemperature of 40° C.) and kept in such stretched state for 120 minutesis represented by S2. A stress retention represented by a ratio of S2/S1is preferably 0.2 or higher. The nonwoven fabric layers 8, 9 having suchphysical properties advantageously have a high extensibility, a reliableresistance against deterioration of the stretch stress possiblyoccurring after these layers 8, 9 have been kept in the stretched statefor a long period, and an adequate durability after repeated extensionand contract twice or more often.

As the first and second elastic members 3, 4, natural or syntheticrubber in the form of threads or bands may be used. These elasticmembers 3, 4 preferably have an extensibility of 200-700%. It is alsopossible to use a foam rubber as a stock material for these elasticmembers 3, 4.

The outer sheet 2 may be formed also by a composite sheet consisting ofan elastically stretchable hydrophobic fibrous nonwoven fabric layer andan elastically stretchable, breathable and liquid-impervious plasticfilm placed upon and joined to each other. The film preferably has thesame physical properties as those of the above-described elasticallystretchable nonwoven fabric layer. If the film has its physicalproperties different from those of the nonwoven fabric layer, stretchingratios of these film and nonwoven fabric layer at which they are joinedto each other should be appropriately preadjusted by taking account ofthe respective residual strains peculiar to these film and nonwovenfabric layer so that these film and nonwoven fabric may havesubstantially same dimensions after they have been relaxed.

The outer sheet 2 may be formed also by a composite nonwoven fabriclayer composed of an elastically stretchable hydrophobic fibrousnonwoven fabric layer made of a thermoplastic elastomer resin fibers anda hydrophobic fibrous nonwoven fabric layer made of crimped fibersobtained by a melt spinning thermoplastic synthetic resin such aspolypropylene, polyethylene or polyester, the latter being placed on atleast one surface of the former.

The panel 5 comprises a non-stretchable liquid-pervious topsheet 19lying on a body facing side, a non-stretchable liquid-imperviousbacksheet 20 lying on an undergarment facing side and a liquid-absorbentcore 21 interposed between these top- and backsheets 19, 20. The panel 5has a substantially rectangular planar shape and extends between thefront and rear waist regions 10, 12. The panel 5 has longitudinallyopposite margins 5 a formed by portions of the top- and backsheets 19,20 extending outward beyond longitudinally opposite ends 21 a of thecore 21 in the longitudinal direction and transversely opposite lateralmargins 5 b formed by portions of the top- and backsheets 19, 20extending outward beyond transversely opposite side edges 21 b of thecore 21 in the transverse direction. The top- and backsheets 19, 20 areplaced upon and respective inner surfaces bonded to each other along thelongitudinally opposite margins 5 a and the transversely oppositelateral margins 5 b of the panel 5 by means of adhesive (not shown). Thecore 21 is joined to the respective inner surfaces of the top- andbacksheets 19, 20 by means of adhesive (not shown).

The panel 5 is provided along its lateral margins 5 b with extensibleelastic members 22 extending in the longitudinal direction. Theseelastic members 22 are attached to the lateral margins 5 b understretching in the longitudinal direction at a given ratio and arecontractile in the longitudinal direction. The elastic members 22 areinterposed between the top- and backsheets 19, 20 and secured to therespective inner surfaces of these sheets 19, 20 by means of adhesive(not shown). The lateral margins 5 b are formed with a plurality ofirregular wrinkles or gathers due to contraction of the elastic members22.

The panel 5 has its longitudinally opposite margins 5 a attached to theouter sheet 2 and its middle zone 5 c attached to the lower margins 16of the respective outer sheet sections in the crotch region. The outersurface of the backsheet 20 constituting the panel 5 is joined to theouter surface of the nonwoven fabric layer 8 constituting the outersheet 2 by means of adhesive 23. Except the longitudinally oppositemargins 5 a and the middle zone 5 c, the panel 5 is not joined to theouter sheet 2 and free with respect thereto. Preferably, thelongitudinally opposite margins 5 a are partially joined to the sheet 2.

To obtain a pants-configuration from the planar state shown by FIG. 1,the crotch region 11 is folded with the panel 5 inside, then the outersheet sections 2 a, 2 b in the respective waist regions are put flattogether along the waist regions' lateral margins 14 and bonded togetherin the vicinity of the side edges 17 of these waist regions' lateralmargins 14 by means of a plurality of welding lines 18 (See FIG. 1).

In the article 1, the outer sheet 2 is formed with none of wrinkles orgathers along the waist regions' upper margins 13 as well as along thecrotch region's lateral margins 15. Thus both the waist regions' uppermargins 13 and the crotch region's lateral margins 15 are substantiallyplanar and gaps will not be formed between the wearer's body and thewaist regions' upper margins 13 and/or the crotch region's lateralmargins 15 as the article 1 is worn. In this way, there is nopossibility that bodily discharges might leak along the waist regions'upper margins 13 and/or the crotch region's lateral margins 15. Thewaist regions' upper margins 13 and the crotch region's lateral margins15 are free from wrinkles or gathers and therefore the article 1 willnot give the wearer uncomfortable feeling as the article 1 is worn.Furthermore, the first elastic members 3 and the elastic members 22extend so as to form rings as the article 1 is worn and thereby to bringthe peripheries of the leg-openings in close contact with entirecircumferences of the wearer's legs.

FIG. 5 is a plan view of the outer sheet 2. In the outer sheet 2, astretch stress in the second elastic members 4 is higher than that inthe first elastic members 3. In the outer sheet 2, a transverse stretchstress in the waist regions' upper margins 13 is higher than aleg-circumferential stretch stress in the crotch region's lateralmargins 15 as well as than a transverse stretch stress in the portion ofthe sheet 2 except the waist regions' upper margins 13 and the crotchregion's lateral margins 15. In addition, a leg-circumferential stretchstress in the crotch region's lateral margins 15 is also higher than thetransverse stretch stress in the portion of the sheet 2 except the waistregions' upper margins 13 and the crotch region's lateral margins 15. Itis preferable for the outer sheet 2 that the transverse stretch stressin the waist regions' upper margins 13 is in a range of 0.2-0.6N/25 mm,the leg-circumferential stretch stress in the crotch region's lateralmargins 15 is in a range of 0.1-0.4N/25 mm and the transverse stretchstress in the above-described portion 24 is in a range of 0.08-0.35N/25mm. These values of stretch stress correspond to those obtained as theouter sheet 2 is stretched together with the elastic members 3, 4 by110-120%.

If the stretch stress in the waist regions' upper margins 13 of theouter sheet 2 is less than that in the crotch region's lateral margins15, specifically less than 0.2N/25 mm, movement of the wearer's legs istransmitted to the crotch region's lateral margins 15 so as to shiftthese crotch region's lateral margins 15 which, in turn, shift the waistregions' upper margins 13. Consequently, the article 1 is apt to slipdown along the wearer's waist. On the contrary, if the stretch stress inthe waist regions' upper margins 13 exceeds 0.6N/25 mm and the stretchstress in the portion 24 exceeds 0.35N/25 mm, the waist regions' uppermargins 13 and the portion 24 will endurably tighten the wearer's waistand give the wearer uncomfortable feeling.

If the stretch stress in the crotch region's lateral margins 15 is lessthan 0.1N/25 mm, these crotch region's lateral margins can notadequately fit around the wearer's legs and it is apprehended that bodydischarges might leak out from these crotch region's lateral margins 15.If the stretch stress in the crotch region's lateral margins 15 exceeds0.4N/25 mm, these crotch region's lateral margins will excessivelytighten the wearer's legs and movement of the legs will be restrained bythese crotch region's lateral margins 15.

FIG. 6 is a diagram schematically illustrating an example of aproduction line for the outer sheet 2, FIG. 7 is a plan view of thesheet 2 before it is bisected and FIG. 8 is a diagram illustrating amanner in which the panel 5 is attached to the outer sheet 2. In FIG. 6,a longitudinal direction is indicated by an arrow L and a transversedirection is indicated by an arrow M.

On the production line, the nonwoven fabric layers 8, 9 as well as thefirst and second elastic members 3, 4 are continuously running in thelongitudinal direction indicated by an arrow L1 under a predeterminedtension in the longitudinal direction thereof. On this production line,the first elastic members 3 extend at an angle of approximately 30-40°with respect to a longitudinal center line 25 of the outer sheet 2. Twogroups of the first elastic members 3 repeat separation and intersectionin the transverse direction of the outer sheet 2 so as to describezigzag lines in the longitudinal direction of the sheet 2. The secondelastic members 4 extend in parallel to the longitudinal center line 25and describe substantially straight lines.

On the production line, the stretching ratios at which the elasticmembers 3, 4 and the nonwoven fabric layers 8, 9 (i.e., the outer sheet)are stretched are preadjusted to ensure that these elastic members 3,4and nonwoven fabric layers 8, 9 may exhibit substantially same residualstrains. The elastic members 3, 4 are interposed between these nonwovenfabric layers 8, 9 and secured to respective surfaces of these nonwovenfabric layers 8, 9 opposed to each other. Though not shown, adhesive isintermittently applied on at least one of these opposed surfaces of thenonwoven fabric layers 8, 9.

After the elastic members 3, 4 have been secured to the outer sheet 2,regions 26 enclosed by the first elastic members are cut out from thesheet 2 and then the sheet 2 is cut together with the elastic members 3,4 along first cutting lines 27 extending in the transverse direction toobtain the outer sheet 2 of FIG. 7.

The individual outer sheet 2 of FIG. 7 obtained in the previous step isthen cut along second cutting lines 28 extending on both sides of thecenter line 25 and thereby a transversely middle zone is cut out so asto divide the individual outer sheet 2 into the first and second outersheet sections 2 a, 2 b. After divided, the first and second sheetsections 2 a, 2 b are spaced from each other by a given dimension in thetransverse direction and the panel 5 is joined to the inner surfaces ofthese sheet sections 2 a, 2 b. The dimension by which these sheetsections 2 a, 2 b are spaced from each other in the crotch region 11 ispreferably in a range of 4-6 cm.

A stock material for the topsheet 19 may be selected from a groupconsisting of a hydrophilic fibrous nonwoven fabric layer, a hydrophobicfibrous nonwoven fabric layer having a plurality of perforations and aplastic film having a plurality of fine perforations. A stock materialfor the backsheet 20 may be selected from a group consisting of ahydrophobic fibrous nonwoven fabric layer, a breathableliquid-impervious plastic film, a composite nonwoven fabric layercomprising two hydrophobic fibrous nonwoven fabric layers laminated oneach other and a composite sheet comprising a hydrophobic fibrousnonwoven fabric layer and a breathable liquid-impervious plastic filmlaminated on each other. It is also possible to form the backsheet 20using a melt blown fibrous nonwoven fabric layer having a highwater-resistance and a spun bond fibrous nonwoven fabric layer having ahigh strength and a high flexibility laminated on at least one surfaceof the former.

The nonwoven fabric forming the top- and backsheets 19, 20 may beselected from a group consisting of products obtained by spun lace-needle punch-, melt blown-, thermal bond-, spun bond- and chemicalbond-processes. The component fibers of the nonwoven fabric may beselected from a group consisting of polyolefin-, polyester- andpolyamide-based fibers, and core-and-sheath type or side-by-side typeconjugated fibers of polyethylene/polypropylene orpolyethylene/polyester.

The core 21 comprises a mixture of fluff pulp and super-absorbentpolymer particles or a mixture of fluff pulp, super-absorbent polymerparticles and thermoplastic synthetic resin fibers, in any case,compressed to a desired thickness. Preferably, the core 21 is entirelycovered with a liquid-pervious sheet such as a tissue paper or ahydrophilic fibrous nonwoven fabric layer in order to prevent the core21 from getting out of its initial shape and/or to prevent any quantityof the polymer particles from falling off from the core 21. The adhesivemay be selected from a group consisting of hot melt adhesive,acryl-based adhesive and rubber-based adhesive.

Joining of the sheets 2, 19, 20 one to another, attaching the elasticmembers 3, 4 to the sheet 2 and fixation of the core 21 to the sheets19, 20 may be carried out using welding technique such as heat-sealingand sonic sealing.

The pants-type disposable wearing article according to this invention isprimarily characterized in that the elastically stretchable outer sheetand the first elastic members attached to the crotch region's lateralmargins have substantially same leg-circumferential dimensions withoutformation of any wrinkles or gathers after these outer sheet and firstelastic members are relaxed. In this way, there is no possibility thatany gap might be formed between the wearer's skin and the crotchregion's lateral margins and any quantity of bodily discharges mightleak out beyond these crotch region's lateral margins. In this article,the crotch region's lateral margins are substantially planar and it isnot apprehended that the wearer might experience any uncomfortablefeeling. In this article, the outer sheet cooperates with the firstelastic members to achieve good fitness around the wearer's legs so thatthe crotch region's lateral margins may come in close contact with thewearer's legs and reliably prevent any quantity of bodily dischargesfrom leaking out beyond these crotch region's lateral margins.

Similarly, the second elastic members are attached to the waist regions'upper margins of the outer sheet so that the outer sheet and the secondelastic members may have substantially same transverse dimensionswithout formation of a plurality of irregular wrinkles or gathers afterthese outer sheet and second elastic members are relaxed. In this way,there is no possibility that any gap might be formed between thewearer's skin and the waist regions' upper margins and any quantity ofbodily discharges might leak out beyond these waist regions' uppermargins. In this article, the waist regions' upper margins aresubstantially planar and it is not apprehended that the wearer mightexperience any uncomfortable feeling. In this article, the outer sheetcooperates with the second elastic members to achieve good fitnessaround the wearer's waist and thereby to prevent the article fromslipping down along the wearer's waist.

1. A pants-type disposable wearing article comprising an elasticallystretchable outer sheet defining front and rear waist regions opposed toeach other and a crotch region extending between these waist regions,and a liquid-absorbent panel attached to an inner surface of said outersheet and extending between said front and rear waist regions, saidouter sheet having waist regions' upper margins extending in said frontand rear waist regions in a transverse direction, waist-circumferentiallateral margins extending in a longitudinal direction and crotchregion's lateral margins extending in said crotch region in theleg-circumferential direction, said front and rear waist regions beingconnected along said waist-circumferential margins so as to define awaist-opening and a pair of leg-openings, and first elastic membersextending in the leg-circumferential direction are attached to saidcrotch region's lateral margins of said outer sheet, said pants-typedisposable wearing article further comprising: said outer sheet and saidfirst elastic members being joined together while said outer sheet beingstretched at a given stretching ratio in the transverse direction andsaid first elastic members being stretched at a given stretching ratioin the leg-circumferential direction so as to ensure that said outersheet and said first elastic members have substantially same dimensionsas measured in the leg-circumferential direction after these outer sheetand first elastic members have been relaxed and that said crotchregion's lateral margins are substantially planar without undulation ina thickness direction of said outer sheet; wherein said outer sheetcomprises zones which underlie and are coextensive with the firstelastic members, said zones being wrinkle-free when said outer sheet andsaid first elastic members are all relaxed; and wherein a peripheraledge of each of said leg-openings comprises a wrinkle-free sectiondefined by one of said zones, and a wrinkled section defined by anassociated one of transversely opposite edges of the panel, saidtransversely opposite edges of the panel having further elastic membersattached thereto.
 2. The wearing article according to claim 1, whereinwaist-circumferential second elastic members extending in the transversedirection are attached to the waist regions' upper margins of said outersheet and said outer sheet and said second elastic members are joinedtogether while said outer sheet is stretched at a given stretching ratioand said second elastic members are stretched at a stretching ratio bothin the transverse direction so as to ensure that said outer sheet andsaid second elastic members have substantially the same dimensions asmeasured in the transverse direction after these outer sheet and secondelastic members have been relaxed and that said waist regions' uppermargins are substantially planar without undulation in a thicknessdirection of said outer sheet.
 3. The wearing article according to claim2, wherein a transverse stretch stress in the waist regions' uppermargins of said outer sheet is higher than a leg-circumferential stretchstress in the crotch region's lateral margins of said outer sheet andalso than a transverse stretch stress in a portion of said outer sheetexcept said waist regions' upper margins and said crotch regiont'slateral margins.
 4. The wearing article according to claim 2, whereinsaid outer sheet is formed by a composite nonwoven fabric layer composedof two elastically stretchable hydrophobic fibrous nonwoven fabriclayers placed upon each other, and said first and second elastic membersform no part of and are interposed between said nonwoven fabric layers.5. The wearing article according to claim 2, wherein said outer sheet isformed by a composite sheet composed of an elastically stretchablehydrophobic fibrous nonwoven fabric layer and a breathableliquid-impervious plastic film joined together, and said first andsecond elastic members form no part of and are interposed between saidnonwoven fabric layer and said film.
 6. The wearing article according toclaim 2, wherein said zones underlie and are coextensive with both thefirst and second elastic members; and when said outer sheet and saidfirst and second elastic members are all relaxed, the first and secondelastic members have the same dimensions as the respective said zoneswhich are thereby wrinkle-free.
 7. The wearing article according toclaim 1, wherein said panel comprises a liquid-pervious topsheet lyingon a body facing side, a liquid-impervious backsheet lying on anundergarment facing side and a liquid-absorbent core interposed betweensaid top-and backsheets.
 8. A pants-type disposable wearing article,comprising: elastically stretchable front and rear outer sheets eachbeing contoured by an upper edge, a lower edge and transversely oppositelateral edges connecting the upper and lower edges, each of saidtransversely opposite lateral edges comprising an upper section adjacentto the upper edge and a lower section adjacent to the lower edge; aliquid-absorbent panel having longitudinally opposite ends attached tosaid front and rear outer sheets, respectively, thereby connecting saidfront and rear outer sheets together; the upper sections of thetransversely opposite lateral edges of said front and rear outer sheetsbeing bonded to each other to define a waist hole and a pair of legholes; the upper edges of said front and rear outer sheets togetherdefining a peripheral edge of said waist hole; the lower sections of thetransversely opposite lateral edges of said front and rear outer sheetsdefining at least partially peripheral edges of said leg holes; andfirst elastic members bonded to and along the lower sections of thetransversely opposite lateral edges of said front and rear outer sheetsto extend in circumferential directions of said leg holes; wherein thepanel is directly attached to the outer sheets only at thelongitudinally opposite ends of said panel and at the lower edges ofsaid outer sheets; said first elastic members and the lower sections arebonded to each other when said first elastic members and outer sheetsare stretched; and when said first elastic members and outer sheets areall relaxed, a dimension of each said first elastic member as measuredin the circumferential direction of the respective leg holes issubstantially same as that of the respective lower section whichunderlies and is coextensive with said first elastic member, and saidlower sections are thereby wrinkle free.
 9. The wearing articleaccording to claim 8, further comprising second elastic members bondedto and along the upper edges of said front and rear outer sheets toextend in a circumferential direction of said waist hole; wherein saidsecond elastic members and the upper edges are bonded to each other whensaid second elastic members and outer sheets are stretched; and whensaid second elastic members and outer sheets are all relaxed, adimension of each said second elastic member as measured in thecircumferential direction of said waist hole is substantially same asthat of the respective upper edge which underlies and is coextensivewith said second elastic member, and said upper edges are therebywrinkle free.
 10. The wearing article according to claim 9, wherein eachof said outer sheets has a transverse stretch stress along the upperedge higher than a leg circumferential stretch stress along the lowersections; and the transverse stretch stress of each of said outer sheetsalong the upper edge is higher than that in a zone located outside theupper edge and the lower sections.
 11. The wearing article according toclaim 9, wherein each of said outer sheets comprises a composite sheetcomposed of two elastically stretchable hydrophobic fibrous nonwovenfabric layers joined together, and said first and second elastic membersform no part of and are interposed between said nonwoven fabric layers.12. The wearing article according to claim 9, wherein each of said outersheets comprises a composite sheet composed of an elasticallystretchable hydrophobic fibrous nonwoven fabric layer and a breathableliquid-impervious plastic film joined together, and said first andsecond elastic members form no part of and are interposed between saidnonwoven fabric layer and said film.
 13. The wearing article accordingto claim 9, wherein each of said outer sheets is one of (a) a compositesheet composed of two elastically stretchable hydrophobic fibrousnonwoven fabric layers joined together, wherein said first and secondelastic members form no part of and are interposed between said nonwovenfabric layers; and (b) a composite sheet composed of an elasticallystretchable hydrophobic fibrous nonwoven fabric layer and a breathableliquid-impervious plastic film joined together, wherein said first andsecond elastic members form no part of and are interposed between saidnonwoven fabric layer and said film.
 14. The wearing article accordingto claim 13, wherein in each of said outer sheets (i) a transversestretch stress along the upper edge, which is oriented in a transversedirection of the article, is higher than a leg circumferential stretchstress along the lower sections, which are oriented obliquely to thetransverse direction; (ii) the transverse stretch stress along the upperedge is than that in a middle zone of the outer sheet that is locatedbetween the upper edge and the lower sections; and (iii)the legcircumferential stretch stress along the lower sections is higher thanthe transverse stretch stress in said middle zone of the outer sheet.15. The wearing article according to claim 13, wherein the lower edgesof the outer sheets are exposed on an external surface of the article ina crotch region of the article.
 16. The wearing article according toclaim 13, wherein the peripheral edge of each of said leg holes ispartially wrinkle-free in a first section defined by the lower sectionsof the respective transversely opposite lateral edges the outer sheets,and partially wrinkled in a second section defined by an associated oneof transversely opposite edges of the panel, said transversely oppositeedges of the panel having third elastic members attached thereto.